add_subdirectory: Compute output dir with consistent slashes (#10072)

When the command is invoked without an explicit build directory path we
compute it from the source directory path.  When either the source or
build tree is the root of a Windows drive letter it will have a trailing
slash.  Handle slashes consistently when substituting the current output
directory for the current source directory.

While at it, use cmSystemTools::IsSubDirectory instead of FindLastString
to verify that the source directory is a subdirectory.

Inspired-by: Graham Menhennitt <graham@menhennitt.com.au>

1 files changed, 10 insertions, 5 deletions

diff --git a/Source/cmAddSubDirectoryCommand.cxx b/Source/cmAddSubDirectoryCommand.cxx
index 9efeda4..5b1c9c6 100644
--- a/Source/cmAddSubDirectoryCommand.cxx
+++ b/Source/cmAddSubDirectoryCommand.cxx
@@ -78,7 +78,7 @@ bool cmAddSubDirectoryCommand::InitialPass
     // No binary directory was specified.  If the source directory is
     // not a subdirectory of the current directory then it is an
     // error.
-    if(!cmSystemTools::FindLastString(srcPath.c_str(),
+    if(!cmSystemTools::IsSubDirectory(srcPath.c_str(),
                                       this->Makefile->GetCurrentDirectory()))
       {
       cmOStringStream e;
@@ -93,10 +93,15 @@ bool cmAddSubDirectoryCommand::InitialPass
 
     // Remove the CurrentDirectory from the srcPath and replace it
     // with the CurrentOutputDirectory.
-    binPath = srcPath;
-    cmSystemTools::ReplaceString(binPath,
-                                 this->Makefile->GetCurrentDirectory(),
-                                 this->Makefile->GetCurrentOutputDirectory());
+    const char* src = this->Makefile->GetCurrentDirectory();
+    const char* bin = this->Makefile->GetCurrentOutputDirectory();
+    size_t srcLen = strlen(src);
+    size_t binLen = strlen(bin);
+    if(srcLen > 0 && src[srcLen-1] == '/')
+      { --srcLen; }
+    if(binLen > 0 && bin[binLen-1] == '/')
+      { --binLen; }
+    binPath = std::string(bin, binLen) + srcPath.substr(srcLen);
     }
   else
     {